1. Technical Field
The present disclosure relates to systems and methods for providing energy to biologic tissue and, more particularly, to an electrosurgical instrument for performing surface coagulation and dissection of biologic tissue.
2. Background of Related Art
Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal, laser, etc.) are applied to tissue to achieve a desired result. Electrosurgery involves application of high radio frequency electrical current to a surgical site to cut, ablate, coagulate or seal tissue. In monopolar electrosurgery, a source or active electrode delivers radio frequency energy from the electrosurgical generator to the tissue and a return electrode carries the current back to the generator. In monopolar electrosurgery, the source electrode is typically part of the surgical instrument held by the surgeon and applied to the tissue to be treated. A patient return electrode is placed remotely from the active electrode to carry the current back to the generator. In tissue ablation electrosurgery, the radio frequency energy may be delivered to targeted tissue by an antenna or probe.
There are several types of microwave antenna assemblies in use, e.g., monopole, dipole and helical, which may be used in tissue ablation applications. In monopole and dipole antenna assemblies, microwave energy generally radiates perpendicularly away from the axis of the conductor. Monopole antenna assemblies typically include a single, elongated conductor. A typical dipole antenna assembly includes two elongated conductors, which are linearly aligned and positioned end-to-end relative to one another with an electrical insulator placed therebetween. Helical antenna assemblies include a helically-shaped conductor connected to a ground plane. Helical antenna assemblies can operate in a number of modes including normal mode (broadside), in which the field radiated by the helix is maximum in a perpendicular plane to the helix axis, and axial mode (end fire), in which maximum radiation is along the helix axis. The tuning of a helical antenna assembly may be determined, at least in part, by the physical characteristics of the helical antenna element, e.g., the helix diameter, the pitch or distance between coils of the helix, and the position of the helix in relation to the probe assembly to which it is mounted.
The typical microwave antenna has a long, thin inner conductor that extends along the longitudinal axis of the probe and is surrounded by a dielectric material and is further surrounded by an outer conductor around the dielectric material such that the outer conductor also extends along the axis of the probe. In another variation of the probe that provides for effective outward radiation of energy or heating, a portion or portions of the outer conductor can be selectively removed. This type of construction is typically referred to as a “leaky waveguide” or “leaky coaxial” antenna. Another variation on the microwave probe involves having the tip formed in a uniform spiral pattern, such as a helix, to provide the necessary configuration for effective radiation. This variation can be used to direct energy in a particular direction, e.g., perpendicular to the axis, in a forward direction (i.e., towards the distal end of the antenna), or combinations thereof. In the case of tissue ablation, a high radio frequency electrical current in the range of about 500 MHz to about 10 GHz is applied to a targeted tissue site to create an ablation volume, which may have a particular size and shape. Ablation volume is correlated to antenna design, antenna tuning, antenna impedance and tissue impedance.
Certain surgical procedures require use of a cutting instrument, e.g., a scalpel or shears, to resect tumors and/or other necrotic lesions, which may necessitate severing one or more blood vessels and thus cause undesirable bleeding. Such bleeding may, in turn, obscure a surgeon's view of the surgical site and generally require the surgeon to attend to controlling the bleeding, rather than to the primary surgical objective(s). This, in turn, may lead to increased operative times and suboptimal surgical outcomes.